Technical Field
The present invention relates to an endoscope.
Description of the Related Art
In the related art, an endoscope, which captures an image of an internal organ of a patient's body or an inside of equipment or a structure, comes into wide use in the medical field or the industrial field. Light from an imaged site is imaged on a light-receiving area of an image sensor in an insertion part of this type of endoscope, which is inserted into an observed object, by an objective lens system. The endoscope converts the image forming light into electrical signals, and transmits the electrical signals, which are video signals, to an external image processing apparatus or the like via a signal cable.
In an endoscope used in the medical field, it becomes important that a thinner outer diameter of a distal insertion part inserted into the body of a patient is required so as to reduce a burden on the patient. In the related art, typically, the maximum outer diameter of a peroral endoscope is approximately 8 mm to approximately 9 mm. For this reason, during insertion, the peroral endoscope may be likely to come into contact with a tongue root, or may cause a patient to feel nausea or dyspnea. In recent years, a thin nasal endoscope quickly comes into wide use. The maximum outer diameter of the thin nasal endoscope is approximately one half of that of the peroral endoscope, that is, is approximately 5 mm to approximately 6 mm. For this reason, the thin nasal endoscope can be inserted into the nose. In many cases, since the maximum outer diameter is approximately 5 mm, which is thin, the thin nasal endoscope less causes vomiting reflex, and the insertion of the thin nasal endoscope does not matter much.
An electronic endoscopic system 501 disclosed in WO2013/031276 and illustrated in FIG. 33 mainly includes an endoscope 503; a light source device 505; a video processor 507; and a monitor 509. The endoscope 503 is configured to include a long and elongated insertion part 511; an operation unit 513; and a universal cable 515 which is an electric cable. The insertion part 511 of the endoscope 503 is configured to include a distal portion 517, a curved portion 519, and a flexible tubular portion 521 which are disposed sequentially from a distal side inserted into a patient. The operation unit 513 is configured to include an operation unit body 523, and a treatment tool channel insertion portion 525 through which various treatment tools are inserted into the insertion part 511. A curve operation knob 527 is disposed in the operation unit body 523 so as to curve the curved portion 519. The curve operation knob 527 includes a UD curve operation knob 529 that curves the curved portion 519 in an upward and downward direction, and an RL curve operation knob 531 that curves the curved portion 519 in a rightward and leftward direction.
An endoscope 533 disclosed in WO2013/146091 and illustrated in FIG. 34 includes an outer barrel 535 in a distal portion. An image mechanism 539 is provided on the outer barrel 535, and is covered with a filling light shielding material 537. The image mechanism 539 includes an image sensor 543 including a light-receiving portion 541 on one surface thereof; a cover member 545 that covers the surface on which the light-receiving portion 541 of the image sensor 543 is provided; a lens unit 547 that is optically combined to the light-receiving portion 541 of the image sensor 543; and a flexible printed wiring board 549. The lens unit 547 includes an objective cover member 551; an aperture stop 553; a plano-convex lens 555; a plan-convex lens 557; and a lens barrel 559 that fixes together these components which are disposed sequentially from an objective side. The plano-convex lens 557 is fixed to the cover member 545 with a bonding agent 561.
A further reduction in the outer diameter of an endoscope (for example, the thinning of the outer diameter of the distal insertion part disclosed in WO2013/031276, or of an insertion part on the objective side disclosed in WO2013/146091) is required. The further reduction in the outer diameter is based on such a medial demand that an operator desires to insert an endoscope into a site (for example, a very thin duct or hole such as a blood vessel) of the body of a patient into which it is difficult to insert existing thin nasal endoscopes including the aforementioned existing thin nasal endoscopes, and to observe the inside of the site in detail.
It is estimated from the exterior of the endoscope 503 (for example, a so-called flexible endoscope in which the insertion part 511 is flexible such that the insertion part 511 can be inserted into a digestive organ in the upper or lower part of a living body) illustrated in FIG. 1 and description of application examples in WO2013/031276 that the endoscope 503 disclosed in WO2013/031276 is an endoscope which is inserted into mainly a digestive tract of a human body. For this reason, it is difficult to insert the endoscope 503 into a very thin duct or hole such as a blood vessel of a human body, and to observe the inside of the duct or hole via the endoscope 503.
In the endoscope 533 disclosed in WO2013/146091, the sizes of the image sensor 543 and the flexible printed wiring board 549 of the image mechanism 539 are larger in a radial direction than the outer diameter of the lens barrel 559. In addition, the endoscope 533 is configured such that the outer barrel 535 accommodates the image mechanism 539 including these members, and the image mechanism 539 is covered with the light shielding material 537 with which the outer barrel 535 is filled. For this reason, a protrusion distance of the image sensor 543 and the flexible printed wiring board 549 which protrude outward from the lens barrel 559 in the radial direction, and the thickness of the outer barrel 535 are disadvantageous to a reduction of the size of the endoscope 533. Since the outer barrel 535 is required, the number of components increases, and the cost increases.